7 Descriptive Statistics Free Online FlashCards

What do descriptive statistics show—and what can’t they establish?

Descriptive statistics organize and summarize observed data; by themselves, they do not establish causes or prove that a pattern holds for a larger population.

How do you calculate a category’s relative frequency?

Relative frequency is the category frequency divided by the total number of observations: $\frac{\text{category frequency}}{\text{total number of observations}}$.

When should you use COUNTIFS instead of COUNTIF?

`COUNTIF` counts cells that match one criterion; `COUNTIFS` counts observations that meet multiple criteria.

How is the mean calculated, and what can pull it toward an extreme?

The mean is the sum of all values divided by the number of values. Because it uses every value, an unusually high or low observation can pull it toward that extreme.

How do you calculate the range, and which values determine it?

The range is the maximum value minus the minimum value. It depends only on the two extremes.

When should you use sample versus population standard deviation?

Use sample standard deviation when observations are a sample used to estimate a larger population; use population standard deviation when the data include the entire population of interest.

Which chart is suitable for comparing category counts or percentages?

A bar chart displays category counts or percentages, making it easy to compare categories.

Why standardize category labels before counting?

Inconsistent labels can cause one category to be counted as separate groups, such as “Online” and “online.” Standardize category labels before counting.

How do you find the median when there are an even number of values?

Sort the values and take the middle one. If there is an even number of observations, take the mean of the two middle values.

What is the mode, and can a data set have multiple modes?

The mode is the most frequently occurring value. A data set can have more than one mode, or none if no value repeats.

What does the interquartile range measure?

The interquartile range is $Q_3-Q_1$, where $Q_1$ and $Q_3$ mark the 25th and 75th percentiles. It describes the spread of the middle half of the observations.

What does standard deviation describe?

Standard deviation measures the typical distance of values from their mean. A small value indicates clustering; a large value indicates greater dispersion.